After you've installed the DevIL libraries you install the gem by going:

gem install devil

If you wish to use the Gosu and TexPlay extensions, it is necessary to also have:

the Gosu gem (gem install gosu)

the TexPlay gem (gem install texplay)

ruby-opengl (gem install ruby-opengl)

For now, there is support for just a subset of DevIL functions, but it is enough
for 95% things you may want to do.

For example uses, see test/ directory
(note: that many of the examples use the Gosu library...this is often just for visualization purposes. Alot of the functionality does not depend on Gosu being present)